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Salt Marsh Mitigation in Connecticut. Typical salt marsh zonation in Connecticut. Tidal gates on Sybil Creek. Mosquito ditching. Some human impacts on salt marshes in Connecticut. Phragmites - invasive sp. Development. Filling in salt marshes. Other notable impacts:

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slide3

Tidal gates on Sybil Creek

Mosquito ditching

Some human impacts on salt marshes in Connecticut

slide5

Filling in salt marshes

Other notable impacts:

undersized culverts beneath roads/bridges

pollution in Long Island Sound

tidal mill ponds (historical impact)

slide6

Tidal Wetlands Act, 1969 - Sec. 22a-28“Preservation of tidal wetlands. Declaration of policy. It is

declared that much of the wetlands of this state has been lost

or despoiled by unregulated dredging, dumping, filling and

like activities and the remaining wetlands of this state are all

in jeopardy of being lost or despoiled by these and other

activities, that such loss of despoliation will adversely affect,

if not entirely eliminate, the value of such wetlands as sources

of nutrients to finfish, crustacea and shellfish of significant

economic value; that such loss or despoliation will destroy

such wetlands as habitats for plants and animals of significant

economic value and will eliminate or substantially reduce

marine commerce, recreation and aesthetic enjoyment; and

that such loss or despoliation will, in most cases, disturb the

natural ability of tidal wetlands to reduce flood damage and

adversely affect the public health and welfare; that such loss

or despoliation will substantially reduce the capacity of such

wetlands to absorb silt and will thus result in the increased

silting of channels and harbor areas to the detriment of free

navigation. Therefore, it is declared to be the public policy of

this state to preserve the wetlands and to prevent the despoliation

and destruction thereof”.

slide7

Salt Marsh restoration in Connecticut

- 1980, DEP Office of Long Island Sound

Programs involved in restoration

- uses federal transportation funding

- impacts of road/bridge construction

- ~1700 acres restored

- increase coastal water productivity

- increase fish production

- enhanced use by herons, shorebirds,

waterfowl

- reduced mosquito-breeding areas

- lessened fire hazards

slide8

Some agencies involved in restoration:

-

Connecticut Department of Environmental

Protection

- Iroquois Gas Transmission System

- Ducks Unlimited

- The Stewart B. McKinney National Wildlife

Refuge

- U.S. Fish and Wildlife Service

- local government

- Audubon Society

- The Nature Conservancy

slide9

Restoration might consist of:

- Phragmites australis removal (reed tolerant of

low salinities (< 18 ppt)

other invasives (Purple loosestrife, Typha)

- plugging old grid ditches (former mosquito

control), clearing natural channels

- removing old impoundments

- Integrated Marsh Management

(creation of new ponds, channels,

salt pannes)

- sediment removal

sediment sources

- stormwater discharge

- dredged navigational channels

- recreational marinas

- culvert and flood gate modifications

slide10

RESTORATION RULES OF THUMB

  • re-establishment of regular tidal flushing with
  • saltwater (over 18 parts per thousand of salt)
  • replacement of Phragmites by salt marsh plants
  • - conversion normally occurs over a 5-10 yr
  • period.
  • re-establishment of salt marsh plants proceeds
  • spontaneously if a nearby salt marsh is present to
  • supply a seed source.
  • - In most cases expensive planting or
  • transplanting programs are not necessary.
  • restoration of tidal flows to their pre-disturbance
  • volumes is not always desirable, especially in the
  • case of subsided wetlands.
  • - restoration reduces or eliminates mosquito breeding
  • in subsided marshes.
  • - restoration re-establishes scenic vistas.
slide11

Restoration at Long Beach, Stratford, Ct.

Steward B. McKinney National Wildlife Refuge

slide18

Bioassessments

- Biological integrity – “ability to support and

maintain balanced, integrated, adaptive

community of organisms having a species

composition, diversity, functional

organization comparable to those of

natural habitats within the region”

- use index of biological integrity

- metrics – combination of:

- native plant cover

- algae

- amphibians

- birds

- macroinvertebrates

- fish

Functional assessments – estimate functions – e.g.

water storage, nutrient cycling

slide19

Approaches and methods of tidal restoration at 57 Connecticut DEP sponsored or permitted projects between 1975 and 1999.

slide20

Table 1. Salt marsh tidal restoration sites included in this study

Study sites

Warren et al. 2002. Salt marsh restoration in Connecticut: 20 years of

science and management. Restoration Ecology 10:497-513

slide21

Recovery of salt marsh vegetation after tidal restoration measured as the loss of Phragmites cover up to 1995, the latest complete false color infrared air photo set available.

Dominance by Phragmites decreases following

tidal restoration.

slide22

Figure 2. (A) Mean percent cover and frequency

of occurrence of Spartina alterniflora (Sa) and

Phragmites australis (Pa) along three

Mumford Cove transects sampled in 1992

and 1997, 2 and 7 years after restoration.

Cover (Tukey's test p> 0.05) and frequency

(chi-square p> 0.05) increased for Sa but

not for Pa. (B) Mean elevations (datum = 1992

local mean lower low water) of points along

three Mumford Cove transects sampled in

1992 and 1997 that supported (cover 1%)

Sa and Pa and points that were essentially

free of these species (cover < 1%).

Spartina increases in percent

cover and frequency

by 7 years.

slide23

 (A) Total mean percent cover and frequency of occurrence for all

salt marsh angiosperms along 1996 restoration transects versus transect

mean salinity. Both measures increase with salinity and regressions are

significant. (B) Mean percent cover and frequency of occurrence for

Phragmites australis along 1996 restoration transects versus transect

mean salinity. Both measures decrease with salinity and regressions are

significant. Frequency drops sharply above 26%; curve fitted by hand.

(C) Mean end of season height and stem density of Phragmites australis at

transect soil water wells (n = 27). Height drops with salinity with maximum

salinity ca. 26%; curve fitted by hand. Stem density does not correlate

with salinity.

Changes

in plants

track

salinity

changes

slide24

Figure 4. Relative abundance of Melampus bidentatus in recovering

versus reference regions (mean density on restoration area/associated

reference marsh) of four marshes at Barn Island in relation to the

number of years of recovery. Although these marshes differ from one

another in ways other than years of recovery, data indicate a long

trajectory for full recovery of Melampus populations

Abundance of

a salt marsh

snail

slide25

Figure 5. Relative abundance (recovering/reference) of birds considered

salt marsh specialists (triangles) and salt marsh generalists (circles) at

two recovering Barn Island (BI) marshes (solid) and at Mumford Cove

(MC, open) plotted against years of restoration at the time counts were

conducted. Although these marshes differ from one another in ways other

than years of restoration, data indicate that it may take a decade for

restoration sites to support equivalent populations of marsh specialists.

Also, marsh generalists, whose use declines over time, rapidly occupy

restoration sites.

Marsh

generalists

decrease,

specialists

increase

through time

slide26

Mean recovery rates, seasonal soil water well and peat salinities, and depths to water table for the three rapidly recovering (Hammock River, Long Cove, and Great Meadows) and two slowly recovering (Barn Island and Great Creek) systems.

Slower recovering sites have lower salinities

and deeper depths to water table

slide27

Mean density (no./m2± SE) of six macroinvertebrates in recovering and

reference regions of three marshes at Barn Island, Connecticut that

have been in the process of restoration for different periods of time.

slide28

Fishes and crustaceans caught within mosquito control ditches at Barn Island in the

recovering marsh (IP1) and the adjacent reference marsh (HQ) below impoundment

dike 21 years after restoration and in recreated creeks of the restored Mumford Cove

marsh 8 years after return of tidal flooding.

slide29

Abundance of birds

(average number of

individuals observed

per visit) at the

reference marsh, HQ,

and the restoration

marshes, IP1, IP3 sites at

Barn Island and the MC

Marsh during surveys

conducted in the summers

of 1994, 1995 and 1999.

slide30

Results

  • Restoration of tidal flow initiated decline in
  • Phragmites and Typha re-establishment of tidal salt
  • marsh species
  • - some sites had rapid recover, others slow
  • - important influences
  • - salinity & hydroperiod (major factor)
  • - slow sites had reduced
  • hydroperiods due to
  • flooding frequency
  • constraints
  • -> altered chemistry
slide31

Some salt marsh macroinvertebrates were

  • present in < 5 years; others might require
  • several decades for establishment
  • Characteristic fish species might return early in
  • restoration (8-13 years); many might require a
  • longer period of time to achieve population sizes
  • characteristic of reference salt marshes.
  • - diets appeared similar between restored and
  • reference sites, though quantity
  • of food (gut contents) differed.
slide32

Marsh generalists birds were present ~ 4-5 years

    • following restoration (increased abundance +
    • diversity).
    • - ~ 10 years, Marsh specialists were present,
    • but less abundant than generalists.
    • - Specialists increase through time..

5. Species have different and often independent

recovery rates.

slide33

Take-home message:

  • With appropriate substrate, hydrology, propagules
  • in vicinity  functioning salt marshes can develop,
  • in time…
  • - reestablishing tidal connections are key.
  • - final equilibrium conditions often
  • unrealistic goal.
  • best to start trajectory,
  • recognize it might take
  • decades to attain marsh
  • with conditions similar
  • to reference sites